Thiells was the location of the NY state institution called "Letchworth Village Home for the Feeble Minded and Epileptics ."
It was formed in 1907 and closed in 1996. Coal was brought in to run the facility. I believe the last railroad use was about 1972. Beyond this to Haverstraw was abandoned about 1942. Also in the same area was the Rockland Psychiatric Center near Orangeburg. Formed in 1927, it also had a coal hauling spur several miles long from the Erie's Piermont branch. It remains semi-open today but rail activity also ceased around the same time as Letchworth. Google searches will reveal ghostly ruins on both these properties. There were many other such facilities around the state, many with rail spurs. They are nearly all abandoned with patients now homeless or in jails, all to save money.IMHO.